1. Field of the Invention
The present invention relates generally to personal audio devices such as wireless telephones that include noise cancellation, and more specifically, to a personal audio device in which frequency or direction-dependent characteristics in the ambient sounds are detected and action is taken on the anti-noise signal in response thereto.
2. Background of the Invention
Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as MP3 players and headphones or earbuds, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise canceling using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
Since the acoustic environment around personal audio devices such as wireless telephones can change dramatically, depending on the sources of noise that are present and the position of the device itself, it is desirable to adapt the noise canceling to take into account such environmental changes. However, adaptive noise canceling can be ineffective or may provide unexpected results for certain ambient sounds.
Therefore, it would be desirable to provide a personal audio device, including a wireless telephone, that provides effective noise cancellation in the presence of certain ambient sounds.